U.S. patent number 5,200,756 [Application Number 07/695,279] was granted by the patent office on 1993-04-06 for three dimensional microstrip patch antenna.
This patent grant is currently assigned to NovAtel Communications Ltd.. Invention is credited to Walter Feller.
United States Patent |
5,200,756 |
Feller |
April 6, 1993 |
Three dimensional microstrip patch antenna
Abstract
An antenna assembly comprises a dome-like substrate with a
ground plane layer on the interior surface of the substrate and a
radiative patch on the outer surface of the substrate. The cavity
defined by the substrate is closed off by a base having a
conductive layer that is connected to the ground plane layer,
thereby to isolate the cavity and circuit elements that may be
disposed therein. Preferably the substrate has a polyhedral form
and the radiative patch is a polygon having apex portions that
extend down over the side surface of the substrate to enhance the
sensitivity of the antenna at low elevations.
Inventors: |
Feller; Walter (Airdrie,
CA) |
Assignee: |
NovAtel Communications Ltd.
(Calgary, CA)
|
Family
ID: |
24792376 |
Appl.
No.: |
07/695,279 |
Filed: |
May 3, 1991 |
Current U.S.
Class: |
343/700MS;
343/846 |
Current CPC
Class: |
H01Q
1/3275 (20130101); H01Q 9/0428 (20130101); H01Q
9/0471 (20130101) |
Current International
Class: |
H01Q
1/32 (20060101); H01Q 9/04 (20060101); H01Q
001/38 () |
Field of
Search: |
;343/7MS,846,829,789 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Arai and Goto, "Patch Antenna on Sphere of Broad Beamwidth",
Proceedings of ISAP '89, Aug. 23, 1989. .
Luk and Tam, "Wraparound Patch Antenna on a Spherical Body",
Proceedings of ISAP '89..
|
Primary Examiner: Hille; Rolf
Assistant Examiner: Le; Hoanganh
Attorney, Agent or Firm: Cesari and McKenna
Claims
What is claimed is:
1. An antenna assembly comprising:
A. a dome-like substrate having a surface with a top portion and
side portions extending from said top portion, said side surface
portions defining an opening opposite said top surface portion;
B. a ground plane layer on the interior surface of said
substrate;
C. a radiative layer on the exterior surface of said substrate,
said radiative layer having a central portion on said top surface
portion and apex portions extending from said top surface portion
and down over the side surface portions; and
D. a base contacting said substrate and closing said opening, said
base having a first surface facing the interior of said substrate
and a second surface opposite said first surface.
2. The assembly defined in claim 1 in which said base includes a
conductive layer on said second surface and means electrically
connecting said conductive layer to said ground plane layer,
thereby to electrically isolate the volume bounded by said
substrate and said base.
3. The assembly of claim 2 including:
A. feed means comprising a conductor disposed on said substrate and
connected to said radiative layer for conductive signals to or from
said radiative layer,
B. circuit means including conductors disposed on said first
surface of said base and connected to said feed means for
processing signals received by said antenna assembly.
4. The antenna assembly defined in claim 3 further including means
connected to said feed means to provide a circular polarization
characteristic for said radiative layer.
5. The assembly defined in claim 2 including:
A. feed means including first and second conductors disposed on
said substrate and connected to said radiative layer,
B. conductors in the form of a hybrid disposed on said first
surface of said base, and
C. signal conditioning components disposed within said interior of
said substrate and connected to operate on signals received by said
radiative layer and passed through said hybrid,
D. means connecting said hybrid to said first and second conductors
to provide a circular polarization characteristic for said antenna
assembly.
6. An antenna comprising:
A. a domelike polyhedral substrate having top and side
surfaces,
B. a groundplane layer on the interior surface of said substrate,
and
C. an antenna element on the exterior surface of said substrate,
said antenna element being a polygonal patch having a central
portion on said top surface and apex portions extending from said
central portion down over side surfaces of said substrate.
7. The antenna of claim 6 in which:
A. said substrate is a truncated pyramid having a rectangular top
surface and
B. said patch is rectangular.
8. The antenna of claim 6 in which:
A. said substrate is a truncated tetrahedron having a triangular
top surface and
B. said patch is triangular.
9. The antenna of claim 6 further comprising a base contacting said
substrate and closing the interior thereof, said base having a
first surface facing the interior of said substrate and a second
surface opposite said first surface.
10. The antenna of claim 9 including a conductive layer on said
second surface and means electrically connecting said conductive
layer to said ground plane layer, thereby to electrically isolate
the volume bounded by said substrate and said base.
11. The antenna defined in claim 10 including:
A. feed means including first and second conductors disposed on
said substrate and connected to said radiative layer,
B. conductors in the form of a hybrid disposed on said first
surface of said base, and
C. signal conditioning components disposed within said interior of
said substrate and connected to operate on signals received by said
radiative layer and passed through said hybrid,
D. means connecting said hybrid to said first and second conductors
to provide a circular polarization characteristic for said antenna.
Description
FIELD OF THE INVENTION
This invention relates generally to antennas and more specifically
to a microstrip antenna assembly that includes both an antenna and
signal conditioning circuitry that processes signals received by
the antenna.
BACKGROUND OF THE INVENTION
A conventional microstrip antenna is generally planar and comprises
an antenna element in the form of a conductive layer on one side of
a dielectric substrate layer, and a conductive ground layer on the
opposite side of the substrate.
Antennas of this type are advantageous in a number of applications
because of their relatively low profile and ease of manufacture, as
well as their compatibility with other components implemented in
microstrip configurations.
In prior microstrip antennas, the propagation pattern may be
substantially independent of azimuth at high elevation angles, that
is, for radiation directions that do not depart greatly from the
normal. At low elevations, on the other hand, the sensitivity of
the same antenna may be largely dependent on azimuthal direction
and, in some cases, the antenna is insensitive in all such
directions at low elevations. An example of this characteristic is
a circularly polarized microstrip antenna which, in prior
convention configurations, has reasonable sensitivity with the
desired polarization only at elevations that are relatively close
to the normal.
However, for a number of applications, the antenna must function
effectively over a wide range of elevation angles and, in
particular, it is necessary that the antenna function at relatively
low angles. An example of such an application is an antenna used
with a Global Positioning System receiver. The receiver will
ordinarily receive circularly polarized signals simultaneously from
a number of earth-orbiting satellites having a wide range of
instantaneous elevations.
Receiving antennas usually function in conjunction with signal
conditioning circuit components such as phase shifters, filters,
and amplifiers that may also be arranged in microstrip
configurations. The present invention relates in part to an
assembly of a microstrip antenna and these auxiliary circuit
components in a compact form to facilitate the use of the assembly
in small transportable equipment. An example of such equipment is a
receiver for receiving and processing signals transmitted by the
satellites in the Global Positioning System.
It is therefore an object of this invention to provide a microstrip
antenna that is sensitive to circularly polarized signals over a
wide range of elevation angles.
Another object is to provide an antenna assembly that has a
relatively low cost and provides adequate shielding of auxiliary
components from the environment.
An antenna assembly embodying the invention comprises a microstrip
antenna having a dome-like configuration and a substrate, carrying
the signal conditioning components associated with the antenna,
attached to and closing off the interior of the dome structure. A
radiative patch extends over and down from the top surface of the
substrate. The signal conditioning components, which are thus
disposed within the interior of the dome structure, are
interconnected by microstrip conductors. The ground plane for this
microstrip circuitry is connected to a metallic lining on the
interior surface of the dome structure which serves as the "ground
plane" for the antenna. These two ground planes thus effectively
completely enclose the signal conditioning circuitry and thereby
effectively shield it from the exterior of the assembly.
The dome structure preferably has a polyhedral configuration,
specifically a truncated pyramid, with side surfaces facing in
various azimuthal directions. The radiative patch is preferably
rectangular, with corner portions extending down over the side
surfaces. These corner portions are, in effect, circularly
polarized sub-antennas having substantial sensitivity at low
elevations. Consequently, the overall antenna exhibits good
sensitivity to circularly polarized signals over a wide range of
elevations and in all azimuthal directions.
This arrangement provides for a compact, easily manufactured
assembly. Moreover, the assembly is rugged and the components
thereof are protected from electromagnetic interference and
environmental stress, which makes the assembly highly useful for a
number of applications including the Global Positioning System
receivers mentioned above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is an isometric view of an antenna assembly embodying the
comprising an antenna assembled with a printed circuit board
base;
FIG. 1B is a side view of the antenna assembly of FIG. 1A;
FIG. 1C is top view of the antenna assembly of FIG. 1A;
FIG. 1D view of the antenna used in the assembly;
FIG. 2A top view of the printed circuit board base of the antenna
assembly of FIG. 1A;
FIG. 2B is an edge view of the base; and
FIG. 3 is an isometric view of an alternative embodiment of the
invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
As shown in FIGS. 1A-1C, an antenna assembly incorporating the
invention comprises an antenna element in the form of a conductive
layer 12, disposed on a dome-shaped dielectric substrate 13. The
substrate 13 preferably has a polyhedral configuration,
specifically a truncated pyramid having a top surface 14 and
sloping side surfaces 15-18.
FIG. 1D shows the interior of the substrate 13. The inner surface
of the substrate is covered with a metallic layer 25 that serves as
a ground "plane" for the antenna and also as a shield for
components housed in the interior of the dome as described below.
The layer 25 extends beneath the lower edge of the substrate.
Returning to FIGS. 1A-1C, the antenna element 12 comprises a
central portion 12a that, in the illustrative embodiment, covers
the substrate top surface 14. The element 12 also includes wing
portions 12b-12e that extend down along the side surfaces 15-18. As
best seen in FIG. 1C, the layer 12 is an essentially square patch
whose corners have, in effect, been folded down on the substrate
side surfaces 15-18. The dimensions of the square are such as would
be used for a conventional planar patch antenna that is fed at the
midpoints of two of its edges for circular polarization. Thus, as
also shown in FIGS. 1A-1C, feed conductors 27 and 29 extend from
the junctures Of wing portions 12d and 12e, and 12e and 12b,
respectively, to the lower edge of substrate surface 18 and then
under the edge to gaps in the ground plane layer 25 (FIG. 1D). They
thus contact conductive pads 31 and 33 on the top surface of a base
23 (FIG. 2A).
As shown in FIG. 2, the base 23 has a microstrip configuration. The
bottom surface (FIG. 2B) is covered with a groundplane conductor
35. The top surface is covered with a conductive layer 36 except in
those areas containing signal and power conductors. This layer is
in contact with the ground plane layer 25 of the substrate 13. The
conductive layers 35 and 36 are connected together by a layer 37
(FIG. 2B) that extends around the edges of the base 23.
The pads 31 and 33 are connected to a phase shifter 38 in the form
of a square hybrid which combines the signals from the pads and
applies the resultant signal to a conductor 40. Each of the legs 42
has an electrical length of one-quarter wavelength. Thus the
electrical distances from the pads 31 and 33 to the conductor 40
differ by one-quarter wavelength and the phase shifter thereby
provides a 90.degree. relative phase shift to the signals received
from the antenna conductor 12 (FIG. 1A) by way of the pads 31 and
33. The phase shifter also includes a resistive termination 44 at
the remaining corner of the hybrid to prevent undesirable
reflections from that corner.
With this arrangement, the antenna exhibits sensitivity to
circularly polarized signals over a wide range of elevations and,
in particular, at materially lower elevations than planar patch
antennas. Moreover, the entire assembly is compact and of low cost,
and it provides effective shielding of the components contained
therein from the environment.
With further reference to FIG. 2A, the conductor 40 connects to a
narrow-band filter 46 mounted on the base 23. The output of the
filter 46 is applied to a conductor 48, which feeds the filtered
signal from the antenna to an amplifier indicated at 50. The output
of the amplifier 50 is coupled through a capacitor 52 to a
connector 54 extending through the base 23. The connector, in turn,
delivers the RF signal to the demodulation and signal processing
elements (not shown) of a receiver incorporating the antenna
assembly.
The connector 54 also provides power for the amplifier 50, the DC
path to the amplifier including a resistor 56 in parallel with the
capacitor 52.
FIG. 3 depicts another variation of the invention. In this case the
polyhedral dome 70 is a truncated tetrahedron. The antenna layer 72
is essentially a triangular patch that covers the top surface of
the dome, with the apices of the patch extending down over the side
surfaces. In all other respects, the antenna assembly of FIG. 3 is
like that of FIGS. 1 and 2. Thus the antenna layer 72 connects to
feeders (not shown) that provide circular polarization.
The foregoing description has been limited to specific embodiments
of this invention. It will be apparent, however, that variations
and modifications may be made to the invention, with the attainment
of some or all of its advantages. Therefore, it is the object of
the appended claims to cover all such variations and modifications
as come within the true spirit and scope of the invention.
* * * * *